1. Field of the Invention
The present invention relates to a photographic film cassette and a camera for use therewith. More particularly, the invention relates to an improvement of a photographic film cassette in which a leader of a photographic film is caused, by rotation of a spool, to advance to the outside of a cassette shell, and a camera suitable therefor.
2. Description of the Related Art
A conventional photographic film cassette contains a 135-type photographic filmstrip (hereinafter referred to as "film"), having a leader which protrudes from a cassette shell prior to loading a camera therewith. When the camera is loaded with the cassette, the cassette shell is inserted into a cassette receiving chamber at the same time as the leader is widthwise inserted in position within the camera. In order to precisely position the cassette shell within the cassette receiving chamber, various positioning methods are known. For example, Japanese Utility Model Laid-Open Publication No. 49-75340 discloses a device having a positioning portion formed on a cassette shell which is kept in contact with a positioning member disposed in a cassette chamber.
As suggested in U.S. Pat. Nos. 4,834,306 and 4,938,429 and Japanese Patent Laid-Open Publication No. 3-37645 (corresponding to U.S. Ser. No. 07/870,212 and to EP 0 406 815 A2), a known photographic film cassette includes a photographic film positioned so that a leader does not protrude from the cassette shell prior to loading the cassette in a camera. Such a cassette is easily loaded into a camera. A simple film-advancing mechanism of the camera is typically used with this type of cassette and includes a construction which rotates a spool to unwind the photographic film, thereby causing the leader to move through a passageway for the photographic film and exit from the cassette.
There is, however, the possibility of accidental reuse of a cassette of this type because the cassette with the leader fully contained therein in an unused state is indiscernible from one in a used state. It has been suggested, e.g., in U.S. Pat. No. 5,023,642, to utilize a use-condition indicator/lock-out mechanism incorporated in a cassette for indicating a status of the photographic film, either exposed or unexposed, and for preventing the cassette from being reloaded in a camera after the photographic film is fully exposed. The cassette is also provided with a circularly disposed bar code, such as a DX code, for representing sensitivity, a maximum number of photographic frames, and latitude to be transmitted to a camera.
In a leader-advancing cassette, however, the leader may become jammed during initial advancement of the photographic film. This is because the leader might encounter upon a wall or a stepped portion caused by a deviation between a receiving mouth of the camera and the passage mouth as it is advanced out of the cassette shell. Further rotation of the spool in the unwinding direction might cause an increase in jamming at the outside of the passage mouth. This problem is not associated with a conventional leader-protruded cassette in which the leader can be manually inserted in a passage inside the camera without fail.
Such a leader-advancing cassette is also disadvantageous in that it may drop out of the cassette receiving chamber when removing the cassette therefrom after exposure because the cassette may be loaded through a bottom portion of the camera.
A conventional leader-advancing cassette, as described above, has a lock-out mechanism which requires a cooperating structure on the camera for locking out the cassette. The cassette having the use-condition indicator/lock-out mechanism and the circularly disposed bar code, is particularly disadvantageous in that it is so big that a very large camera must be designed therefor. This is inconsistent with the purpose of a leader-advancing cassette, which is convenience.